Showing papers in "European Journal of Applied Physiology in 2018"

Lactate Metabolism: Historical Context, Prior Misinterpretations, And Current Understanding

Abstract: Lactate (La-) has long been at the center of controversy in research, clinical, and athletic settings. Since its discovery in 1780, La- has often been erroneously viewed as simply a hypoxic waste product with multiple deleterious effects. Not until the 1980s, with the introduction of the cell-to-cell lactate shuttle did a paradigm shift in our understanding of the role of La- in metabolism begin. The evidence for La- as a major player in the coordination of whole-body metabolism has since grown rapidly. La- is a readily combusted fuel that is shuttled throughout the body, and it is a potent signal for angiogenesis irrespective of oxygen tension. Despite this, many fundamental discoveries about La- are still working their way into mainstream research, clinical care, and practice. The purpose of this review is to synthesize current understanding of La- metabolism via an appraisal of its robust experimental history, particularly in exercise physiology. That La- production increases during dysoxia is beyond debate, but this condition is the exception rather than the rule. Fluctuations in blood [La-] in health and disease are not typically due to low oxygen tension, a principle first demonstrated with exercise and now understood to varying degrees across disciplines. From its role in coordinating whole-body metabolism as a fuel to its role as a signaling molecule in tumors, the study of La- metabolism continues to expand and holds potential for multiple clinical applications. This review highlights La-'s central role in metabolism and amplifies our understanding of past research.

The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis.

Abstract: Resistance training (RT)-induced skeletal muscle hypertrophy is a highly intricate process. Despite substantial advances, we are far from understanding exactly how muscle hypertrophy develops during RT. The aim of the present review is to discuss new insights related to the role of skeletal muscle damage and muscle protein synthesis (MPS) in mediating RT-induced hypertrophy. Specifically, the thesis that in the early phase of RT (≤ 4 previous RT sessions) increases in muscle cross-sectional area are mostly attributable to muscle damage-induced muscle swelling; then (after ~ 10 sessions), a modest magnitude of muscle hypertrophy ensues; but only during a latter phase of RT (after ~ 18 sessions) is true muscle hypertrophy observed. We argue that the initial increases in MPS post-RT are likely directed to muscle repair and remodelling due to damage, and do not correlate with eventual muscle hypertrophy induced by several RT weeks. Increases in MPS post-RT session only contribute to muscle hypertrophy after a progressive attenuation of muscle damage, and even more significantly when damage is minimal. Furthermore, RT protocols that do not promote significant muscle damage still induce similar muscle hypertrophy and strength gains compared to conditions that do promote initial muscle damage. Thus, we conclude that muscle damage is not the process that mediates or potentiates RT-induced muscle hypertrophy.

The impact of exertional-heat stress on gastrointestinal integrity, gastrointestinal symptoms, systemic endotoxin and cytokine profile

Abstract: The study aimed to determine the effects of exertional-heat stress on gastrointestinal integrity, symptoms, systemic endotoxin and inflammatory responses; and assess the relationship between changes in body temperature and gastrointestinal perturbations. Ten endurance runners completed 2 h running at 60% $$\dot {V}$$ O2max in hot (HOT: 35 °C) and temperate (TEMP: 22 °C)-ambient conditions. Rectal temperature (T re) and gastrointestinal symptoms were recorded every 10 min during exercise. Blood samples were collected pre- and post-exercise, and during recovery to determine plasma intestinal fatty acid binding protein (I-FABP), cortisol, bacterial endotoxin and cytokine profile. Calprotectin was determined from pre- and post-exercise faecal samples. Urinary lactulose:l-rhamnose ratio was used to measure intestinal permeability. Compared with TEMP, HOT significantly increased T re (1.4 ± 0.5 vs 2.4 ± 0.8 °C, p < 0.001), cortisol (26 vs 82%, p < 0.001), I-FABP (127 vs 432%, p < 0.001), incidence (70 vs 90%) and severity (58 counts vs 720 counts, p = 0.008) of total gastrointestinal symptoms. Faecal calprotectin and circulating endotoxin increased post-exercise in both trials (mean increase 1.5 ± 2.5 µg/g, p = 0.032, and 6.9 ± 10.3 pg/ml, p = 0.047, respectively), while anti-endotoxin antibodies increased 28% post-exercise in TEMP and decreased 21% in HOT (p = 0.027). However, intestinal permeability did not differ between trials (p = 0.185). Inflammatory cytokines were greater on HOT compared to TEMP (p < 0.05). Increases in T re were positively associated with I-FABP, IL-10, cortisol, nausea and urge to regurgitate (p < 0.05). Exertional-heat stress induces a thermoregulatory strain that subsequently injures the intestinal epithelium, reduces endotoxin clearance capacity, promotes greater cytokinaemia, and development of gastrointestinal symptoms.

Validity of the Polar V800 monitor for measuring heart rate variability in mountain running route conditions

Abstract: This study was conducted to test, in mountain running route conditions, the accuracy of the Polar V800™ monitor as a suitable device for monitoring the heart rate variability (HRV) of runners Eighteen healthy subjects ran a route that included a range of running slopes such as those encountered in trail and ultra-trail races The comparative study of a V800 and a Holter SEER 12 ECG Recorder™ included the analysis of RR time series and short-term HRV analysis A correction algorithm was designed to obtain the corrected Polar RR intervals Six 5-min segments related to different running slopes were considered for each subject The correlation between corrected V800 RR intervals and Holter RR intervals was very high (r = 099, p 005) and were well correlated (r ≥ 096, p < 0001) Narrow limits of agreement, high correlations and small effect size suggest that the Polar V800 is a valid tool for the analysis of heart rate variability in athletes while running high endurance events such as marathon, trail, and ultra-trail races

Recovery following a marathon: a comparison of cold water immersion, whole body cryotherapy and a placebo control.

Abstract: Cryotherapy is an increasingly popular recovery strategy used in an attempt to attenuate the negative impact of strenuous physical activity on subsequent exercise. Therefore, this study aimed to assess the effects of whole body cryotherapy (WBC) and cold water immersion (CWI) on markers of recovery following a marathon. Thirty-one endurance trained males completed a marathon. Participants were randomly assigned to a CWI, WBC or placebo group. Perceptions of muscle soreness, training stress and markers of muscle function were recorded before the marathon and at 24 and 48 h post exercise. Blood samples were taken at baseline, post intervention and 24 and 48 h post intervention to assess inflammation and muscle damage. WBC had a harmful effect on muscle function compared to CWI post marathon. WBC positively influenced perceptions of training stress compared to CWI. With the exception of C-reactive protein (CRP) at 24 and 48 h, neither cryotherapy intervention positively influenced blood borne markers of inflammation or structural damage compared to placebo. The findings show WBC has a negative impact on muscle function, perceptions of soreness and a number of blood parameters compared to CWI, contradicting the suggestion that WBC may be a superior recovery strategy. Further, cryotherapy is no more effective than a placebo intervention at improving functional recovery or perceptions of training stress following a marathon. These findings lend further evidence to suggest that treatment belief and the placebo effect may be largely responsible for the beneficial effects of cryotherapy on recovery following a marathon.

Determinants, analysis and interpretation of the muscle compound action potential (M wave) in humans: implications for the study of muscle fatigue

Abstract: The compound muscle action potential (M wave) has been commonly used to assess the peripheral properties of the neuromuscular system. More specifically, changes in the M-wave features are used to examine alterations in neuromuscular propagation that can occur during fatiguing contractions. The utility of the M wave is based on the assumption that impaired neuromuscular propagation results in a decrease in M-wave size. However, there remains controversy on whether the size of the M wave is increased or decreased during and/or after high-intensity exercise. The controversy partly arises from the fact that previous authors have considered the M wave as a whole, i.e., without analyzing separately its first and second phases. However, in a series of studies we have demonstrated that the first and second phases of the M wave behave in a different manner during and after fatiguing contractions. The present review is aimed at five main objectives: (1) to describe the mechanistic factors that determine the M-wave shape; (2) to analyze the various factors influencing M-wave properties; (3) to emphasize the need to analyze separately the first and second M-wave phases to adequately identify and interpret changes in muscle fiber membrane properties; (4) to advance the hypothesis that it is an increase (and not a decrease) of the M-wave first phase which reflects impaired sarcolemmal membrane excitability; and (5) to revisit the involvement of impaired sarcolemmal membrane excitability in the reduction of the force generating capacity.

Reliability of tensiomyography and myotonometry in detecting mechanical and contractile characteristics of the lumbar erector spinae in healthy volunteers

Abstract: Tensiomyography™ (TMG) and MyotonPRO® (MMT) are two non-invasive devices for monitoring muscle contractile and mechanical characteristics. This study aimed to evaluate the test–retest reliability of TMG and MMT parameters for measuring (TMG:) muscle displacement (Dm), contraction time (Tc), and velocity (Vc) and (MMT:) frequency (F), stiffness (S), and decrement (D) of the erector spinae muscles (ES) in healthy adults. A particular focus was set on the establishment of reliability measures for the previously barely evaluated secondary TMG parameter Vc. Twenty-four subjects (13 female and 11 male, mean ± SD, 38.0 ± 12.0 years) were measured using TMG and MMT over 2 consecutive days. Absolute and relative reliability was calculated by standard error of measurement (SEM, SEM%), Minimum detectable change (MDC, MDC%), coefficient of variation (CV%) and intraclass correlation coefficient (ICC, 3.1) with a 95% confidence interval (CI). The ICCs for all variables and test–retest intervals ranged from 0.75 to 0.99 indicating a good to excellent relative reliability for both TMG and MMT, demonstrating the lowest values for TMG Tc and between-day MMT D (ICC 0.95, CV < 8%). The reliability for TMG Vc could be established successfully. Its further applicability needs to be confirmed in future studies. MMT was found to be more reliable on repeated testing than the two other TMG parameters Dm and Tc.

The effects of different durations of static stretching within a comprehensive warm-up on voluntary and evoked contractile properties

Abstract: Evidence for performance decrements following prolonged static stretching (SS) has led to a paradigm shift in stretching routines within a warm-up. Rather than SS, dynamic stretching (DS) and dynamic activity (DA) have replaced SS within warm-up routines. The objective of the present study was to compare the effect of differing lower limb SS durations (30 [SS30s], 60 [SS60s] or 120 s [SS120s] of SS per muscle group or no-stretch control) within a comprehensive warm-up protocol consisting of aerobic activity, DS and DA. Sixteen male participants completed the four stretching conditions in a randomized order, after a 5-min low-intensity (cycle) warm-up and before a DS/DA component on separate days. Tests included passive hip and knee ranges of motion (ROM), maximum voluntary knee extensor/flexor force, force produced at 100 ms (F100), vertical jump height and evoked knee extensor contractile properties. For hip flexion (hamstrings) ROM, SS120s provided the largest increase (5.6–11.7%) followed by SS60s (4.3–11.4%), control (4.4–10.6%) and SS30s (3.6–11.1%). For knee flexion (quadriceps) ROM, SS30s provided the largest increase (9.3–18.2%) followed by SS120s (6.5–16.3%), SS60s (7.2–15.2%) and control (6.3–15.2%). There were decreases in quadriceps F100 following SS in SS120s (29.6%) only. There were increases in vertical jump performance in the control (6.2%), SS60s (4.6%) and SS30s (3.3%). While 120 s SS per muscle increased ROM, even within a comprehensive warm-up routine, it also elicited notable performance decrements. However, moderate durations of SS were observed to improve ROM whilst either having negligible or beneficial (but not detrimental) effects on specific aspects of athletic performance.

Changes in fat oxidation in response to various regimes of high intensity interval training (HIIT).

Abstract: Increased whole-body fat oxidation (FOx) has been consistently demonstrated in response to moderate intensity continuous exercise training. Completion of high intensity interval training (HIIT) and its more intense form, sprint interval training (SIT), has also been reported to increase FOx in different populations. An explanation for this increase in FOx is primarily peripheral adaptations via improvements in mitochondrial content and function. However, studies examining changes in FOx are less common in response to HIIT or SIT than those determining increases in maximal oxygen uptake which is concerning, considering that FOx has been identified as a predictor of weight gain and glycemic control. In this review, we explored physiological and methodological issues underpinning existing literature concerning changes in FOx in response to HIIT and SIT. Our results show that completion of interval training increases FOx in approximately 50% of studies, with the frequency of increased FOx higher in response to studies using HIIT compared to SIT. Significant increases in β-HAD, citrate synthase, fatty acid binding protein, or FAT/CD36 are likely responsible for the greater FOx seen in these studies. We encourage scientists to adopt strict methodological procedures to attenuate day-to-day variability in FOx, which is dramatic, and develop standardized procedures for assessing FOx, which may improve detection of changes in FOx in response to HIIT.

Effects of high loading by eccentric triceps surae training on Achilles tendon properties in humans.

Abstract: To document the magnitude and time course of human Achilles tendon adaptations (i.e. changes in tendon morphological and mechanical properties) during a 12-week high-load plantar flexion training program. Ultrasound was used to determine Achilles tendon cross-sectional area (CSA), length and elongation as a function of plantar flexion torque during voluntary plantar flexion. Tendon force–elongation and stress–strain relationships were determined before the start of training (pre-training) and after 4 (post-4), 8 (post-8) and 12 (post-12) training weeks. At the end of the training program, maximum isometric force had increased by 49% and tendon CSA by 17%, but tendon length, maximal tendon elongation and maximal strain were unchanged. Hence, tendon stiffness had increased by 82%, and so had Young’s modulus, by 86%. Significant changes were first detected at post-4 in stiffness (51% increase) and Young’s modulus (87% increase), and at post-8 in CSA (15% increase). Achilles tendon material properties already improved after 4 weeks of high-load training: stiffness increased while CSA remained unchanged. Tendon hypertrophy (increased CSA) was observed after 8 training weeks and contributed to a further increase in Achilles tendon stiffness, but tendon stiffness increases were mostly caused by adaptations in tissue properties.

Vitamin D supplementation attenuates oxidative stress in paraspinal skeletal muscles in patients with low back pain.

Abstract: The aim of the study was to evaluate markers of oxidative stress and vitamin D receptor in paraspinal muscles in low back pain patients with vitamin D deficiency, with normal level of vitamin D, and after 5 weeks of vitamin D supplementation. Patients were divided into three groups: supplemented (SUP) with vitamin D, placebo with normal concentration of vitamin D (SUF), and the placebo group with vitamin D deficiency (DEF). The concentration of serum vitamin D was measured before and after the supplementation with vitamin D (3200 IU/ day for 5 weeks). Markers of lipid and protein peroxidation, the activity of antioxidant enzymes, and protein content of vitamin D receptor was determined in multifidus muscle of patients. Vitamin D supplementation increased serum level of 25(OH)D3 (p < 0.001). In paraspinal muscle level of 8-isoprostanes and protein carbonyls was higher in DEF group as compared to the SUP group (p < 0.05). Antioxidant enzyme activity and vitamin D receptor in paraspinal muscle altered between the groups with different serum vitamin D concentration. The cytosolic superoxide dismutase and glutathione peroxidase activities were significantly higher in DEF group as compared to the SUP group (p < 0.05). An attenuation of markers of free radical damage of lipids and proteins was observed in participants supplemented with Vitamin D. Antioxidant enzyme activities in skeletal muscle differ among patients with different serum vitamin D concentration. Monitoring oxidative stress and VDR protein content might be useful for future studies on the mechanism(s) of vitamin D action in muscle.

Effects of recreational football on women’s fitness and health: adaptations and mechanisms

Abstract: The review describes the fitness and health effects of recreational football in women aged 18–65 years. The review documents that 2 × 1 h of recreational football training for 12–16 weeks causes marked improvements in maximal oxygen uptake (5–15%) and myocardial function in women. Moreover, mean arterial blood pressure was shown to decrease by 2–5 mmHg in normotensive women and 6–8 mmHg in hypertensive women. This review also show that short-term (< 4 months) and medium-term (4–16 months) recreational football training has major beneficial impact on metabolic health profile in women, with fat losses of 1–3 kg and improvements in blood lipid profile. Lastly, 2 × 1 h per week of recreational football training for women elevates lower extremity bone mineralisation by 1–5% and whole-body bone mineralization by 1–2% within 4–12-month interventions. These training adaptations are related to the high heart rates, high number of fast runs, and multiple changes of direction and speed occurring during recreational football training for untrained women. In conclusion, regular small-sided football training for women is an intense and versatile type of training that combines elements of high-intensity interval training (HIIT), endurance training and strength training, thereby providing optimal stimuli for cardiovascular, metabolic and musculoskeletal fitness. Recreational football, therefore, seems to be an effective tool for prevention and treatment of lifestyle diseases in young and middle-aged women, including hypertension, type 2 diabetes and osteopenia. Future research should elucidate effects of football training for elderly women, and as treatment and rehabilitation of breast cancer patients and other women patient groups.

Body position influences arterial occlusion pressure: implications for the standardization of pressure during blood flow restricted exercise

Abstract: Arterial occlusion pressure (AOP) measured in a supine position is often used to set cuff pressures for blood flow restricted exercise (BFRE). However, supine AOP may not reflect seated or standing AOP, thus potentially influencing the degree of occlusion. The primary aim of the study was to investigate the effect of body position on AOP. A secondary aim was to investigate predictors of AOP using wide and narrow cuffs. Twenty-four subjects underwent measurements of thigh circumference, skinfold and blood pressure, followed by assessments of thigh AOP in supine and seated positions with a wide and a narrow cuff, respectively, using Doppler ultrasound. In the supine position, AOP was 148 ± 19 and 348 ± 94 mmHg with the wide and narrow cuff, respectively. This increased to 177 ± 20 and 409 ± 101 mmHg in the seated position, with correlations between supine and seated AOP of R 2 = 0.81 and R 2 = 0.50 for the wide and narrow cuff, respectively. For both cuff widths, thigh circumference constituted the strongest predictor of AOP, with diastolic blood pressure explaining additional variance with the wide cuff. The predictive strength of these variables did not differ between body positions. Our results indicate that body position strongly influences lower limb AOP, especially with narrow cuffs, yielding very high AOP (≥ 500–600 mmHg) in some subjects. This should be taken into account in the standardization of cuff pressures used during BFRE to better control the physiological effects of BFRE.

Classical experiments in whole-body metabolism: open-circuit respirometry-diluted flow chamber, hood, or facemask systems.

Abstract: For over two centuries, scientists have measured gas exchange in animals and humans and linked this to energy expenditure of the body. The aim of this review is to provide a comprehensive overview of open-circuit diluted flow indirect calorimetry and to help researchers to make the optimal choice for a certain system and its application. A historical perspective shows that ‘open circuit diluted flow’ is a technique first used in the 19th century and applicable today for room calorimeters, ventilated hood systems, and facemasks. Room calorimeters are a classic example of an open-circuit diluted flow system. The broadly applied ventilated hood calorimeters follow the same principle and can be classified as a derivative of these room calorimeters. The basic principle is that the subject breathes freely in a passing airflow that is fully captured and analyzed. Oxygen and CO2 concentrations are measured in inlet ambient air and captured outlet air. The airflow, which is adapted depending on the application (e.g., rest versus exercise), is measured. For a room indirect calorimeter, the dilution in the large room volume is also taken into account, and this is the most complex application of this type of calorimeter. Validity of the systems can be tested by alcohol burns, gas infusions and by performing repeated measurements on subjects. Using the latter, the smallest CV (%) was found for repeated VO2max tests (1.2%) with an SD of approximately 1 kJ min−1. The smallest SD was found for sleeping metabolic rate (0.11 kJ min−1) with a CV (%) of 2.4%.

Ultra-shortened time-domain HRV parameters at rest and following exercise in athletes: an alternative to frequency computation of sympathovagal balance.

Abstract: The primary purpose of this study was to determine the accuracy of the standard deviation of normal-to-normal intervals (SDNN) to root mean square of successive normal-to-normal interval differences (RMSSD) ratio from 1-min recordings (SDNN:RMSSD1−min) compared to criterion recordings, as well as its relationship to low-frequency-to-high-frequency ratio (LF:HF) at rest and following maximal exercise in a group of collegiate athletes. Twenty athletes participated in the study. Heart rate variability (HRV) data were measured for 5 min before and at 5–10 and 25–30 min following a maximal exercise test. From each 5-min segment, the frequency-domain measures of HF, LF, and LF:HF ratio were analyzed. Time-domain measures of SDNN, RMSSD, and SDNN:RMSSD ratio were also analyzed from each 5-min segment, as well as from randomly selected 1-min recordings. The 1-min values of SDNN, RMSSD, and SDNN:RMSSD provided no significant differences and nearly perfect intra-class correlations (ICCs ranged from 0.97 to 1.00, p < 0.001 for all) to the criterion measures from 5-min recordings. In addition, SDNN, RMSSD, and SDNN:RMSSD from the 1-min segments provided very large to nearly perfect correlations (r values ranged from 0.71 to 0.97, p < 0.001 for all) to LF, HF, and LF:HF, respectively, at each time point. The findings of the study suggest that ultra-shortened time-domain markers may be useful surrogates of the frequency-domain parameters for tracking changes in sympathovagal activity in athletes.

The Effect of Mental Fatigue on Critical Power during cycling exercise

Abstract: Time to exhaustion (TTE) tests used in the determination of critical power (CP) and curvature constant (W′) of the power–duration relationship are strongly influenced by the perception of effort (PE). This study aimed to investigate whether manipulation of the PE alters the CP and W′. Eleven trained cyclists completed a series of TTE tests to establish CP and W′ under two conditions, following a mentally fatiguing (MF), or a control (CON) task. Both cognitive tasks lasted 30 min followed by a TTE test. Ratings of PE and heart rate (HR) were measured during each TTE. Blood lactate was taken pre and post each TTE test. Ratings of perceived mental and physical fatigue were taken pre- and post-cognitive task, and following each TTE test. Perceived MF significantly increased as a result of the MF task compared to baseline and the CON task (P 0.05). PE was significantly higher during TTE in the MF condition (P 0.05). Neither cognitive task induced any change in CP (MF 253 ± 51 vs. CON 247 ± 58W; P > 0.05), although W′ was significantly reduced in the MF condition (MF 22.8 ± 4.5 vs. CON 29.3 ± 6.3 kJ; P < 0.01). MF has no effect of CP, but reduces the W′ in trained cyclists. Lower lactate accumulation during TTE tests following MF suggests that cyclists were not able to fully expend W′ even though they exercised to volitional exhaustion.

Changes in central and peripheral neuromuscular fatigue indices after concentric versus eccentric contractions of the knee extensors

Abstract: To better understand neuromuscular characteristics of eccentric exercise-induced muscle damage, this study compared between concentric (CONC) and eccentric (ECC) exercises of knee extensor muscles, and the first (ECC1) and second bouts of the eccentric exercise (ECC2) for central and peripheral parameters associated with neuromuscular fatigue. Twelve young men performed three exercise bouts separated by at least 1 week between CONC and ECC1, and 2 weeks between ECC1 and ECC2. In each exercise, maximal voluntary concentric or eccentric contractions of the knee extensors were performed until a reduction in maximal voluntary isometric contraction (MVC) torque of at least 40% MVC was achieved immediately post-exercise. MVC torque, central (voluntary activation and normalised electromyographic activity), and peripheral neuromuscular indices (evoked torque and M-wave amplitude), and muscle soreness were assessed before (PRE), immediately after (POST), 1 h (1H), and 1–4 days after exercise (D1, D2, D3, and D4). MVC torque decreased at only POST for CONC (− 52.8%), but remained below the baseline at POST (− 48.6%), 1H (− 34.1%), and D1–D4 (− 34.1 to − 18.2%) after ECC1, and at POST (− 45.2%), 1H (− 24.4%) and D1 (− 13.4%) after ECC2 (p < 0.05). Voluntary activation decreased immediately after ECC1 (− 21.6%) and ECC2 (− 21.1%), but not after CONC. Electrically evoked torques decreased similarly at POST and 1H for the three conditions, but remained below the baseline at D1 only post-ECC1. These results showed that both central and peripheral factors contributed to the MVC decrease after ECC1 and ECC2, but the decrease was mainly due to peripheral factors after CONC.

Combined resistance and aerobic exercise training reduces insulin resistance and central adiposity in adolescent girls who are obese: randomized clinical trial

Abstract: Exercise training is recommended for improving health and protecting against the development of metabolic and cardiovascular pathologies. Combined resistance and aerobic exercise training (CRAE) has been shown to provide unique benefits in older adults with cardiovascular diseases. We sought to determine the beneficial effects of CRAE in adolescent girls who are obese and hyperinsulinemic. Forty adolescent girls who are obese (age 14.7 ± 1 years; BMI 30 ± 2) were randomly assigned to a “no exercise” (CON n = 20) or combined exercise group (EX n = 20). The EX group performed resistance and aerobic exercise for 12 weeks, 5 times per week. Exercise intensity was increased gradually, from 40 to 70% of heart rate reserve (HRR), every 4 weeks. The brachial-ankle pulse wave velocity (BaPWV), blood pressure (BP), heart rate (HR), blood leptin, adiponectin levels, and body composition were measured before and after the 12-week intervention. We observed that CRAE effectively reduced the body fat percentage, body weight, and waist circumference in the EX group (p < 0.05). After 12 weeks of training, subjects in the CRAE group maintained appropriate leptin and adiponectin levels and showed positive improvements of blood insulin, glucose, and insulin resistance parameters relative to baseline and to the CON group (p < 0.05). CRAE is a useful therapeutic method to alleviate metabolic risk factors in adolescent girls who are obese and hyperinsulinemic.

The effects of a single session of spinal manipulation on strength and cortical drive in athletes

Abstract: The primary purpose of this study was to investigate whether a single session of spinal manipulation (SM) increases strength and cortical drive in the lower limb (soleus muscle) of elite Taekwondo athletes. Soleus-evoked V-waves, H-reflex and maximum voluntary contraction (MVC) of the plantar flexors were recorded from 11 elite Taekwondo athletes using a randomized controlled crossover design. Interventions were either SM or passive movement control. Outcomes were assessed at pre-intervention and at three post-intervention time periods (immediate post, post 30 min and post 60 min). A multifactorial repeated measures ANOVA was conducted to assess within and between group differences. Time and session were used as factors. A post hoc analysis was carried out, when an interactive effect was present. Significance was set at p ≤ 0.05. SM increased MVC force [F(3,30) = 5.95, p < 0.01], and V-waves [F(3,30) = 4.25, p = 0.01] over time compared to the control intervention. Between group differences were significant for all time periods (p < 0.05) except for the post60 force measurements (p = 0.07). A single session of SM increased muscle strength and corticospinal excitability to ankle plantar flexor muscles in elite Taekwondo athletes. The increased MVC force lasted for 30 min and the corticospinal excitability increase persisted for at least 60 min.

Skeletal muscle and performance adaptations to high-intensity training in elite male soccer players: speed endurance runs versus small-sided game training

Abstract: To examine the skeletal muscle and performance responses across two different exercise training modalities which are highly applied in soccer training. Using an RCT design, 39 well-trained male soccer players were randomized into either a speed endurance training (SET; n = 21) or a small-sided game group (SSG; n = 18). Over 4 weeks, thrice weekly, SET performed 6–10 × 30-s all-out runs with 3-min recovery, while SSG completed 2 × 7–9-min small-sided games with 2-min recovery. Muscle biopsies were obtained from m. vastus lateralis pre and post intervention and were subsequently analysed for metabolic enzyme activity and muscle protein expression. Moreover, the Yo–Yo Intermittent Recovery level 2 test (Yo–Yo IR2) was performed. Muscle CS maximal activity increased (P < 0.05) by 18% in SET only, demonstrating larger (P < 0.05) improvement than SSG, while HAD activity increased (P < 0.05) by 24% in both groups. Na+–K+ ATPase α1 subunit protein expression increased (P < 0.05) in SET and SSG (19 and 37%, respectively), while MCT4 protein expression rose (P < 0.05) by 30 and 61% in SET and SSG, respectively. SOD2 protein expression increased (P < 0.05) by 28 and 37% in SET and SSG, respectively, while GLUT-4 protein expression increased (P < 0.05) by 40% in SSG only. Finally, SET displayed 39% greater improvement (P < 0.05) in Yo–Yo IR2 performance than SSG. Speed endurance training improved muscle oxidative capacity and exercise performance more pronouncedly than small-sided game training, but comparable responses were in muscle ion transporters and antioxidative capacity in well-trained male soccer players.

Associations between physical activity, resilience, and quality of life in people with inflammatory bowel disease.

Abstract: Research has shown that moderate-to-vigorous physical activity (MVPA) is associated with higher health-related quality of life (HRQOL) in healthy individuals. Recent studies have suggested that low- to moderate-intensity physical activity can be beneficial to HRQOL in people with inflammatory bowel diseases (IBD); however, studies investigating associations between MVPA and HRQOL in this population are lacking. PURPOSE: To understand the relationships among walking, MVPA, resilience, and HRQOL in people with IBD. People with IBD (n = 242) completed questions about physical activity, resilience and HRQOL. Pearson product-moment correlations and multiple regression analyses were used to identify associations between physical activity and HRQOL. Analysis of covariance was used to compare HRQOL over quartiles of walking and MVPA with demographic variables as covariates. Both walking and MVPA were independently associated with physical (β = 0.21 and β = 0.26, respectively; p ≤ 0.001) but not mental HRQOL (p > 0.05). Higher volumes of MVPA were significantly associated with physical HRQOL (quartile 1 40.3 ± 9.0 vs. quartile 4 47.4 ± 9.0; p < 0.001) while higher volumes of walking were associated with both physical and mental HRQOL (p ≤ 0.01). The findings suggest that engaging in higher volumes of MVPA above 150 min/week and walking, particularly above 60 min/week, are associated with improved HRQOL in people with IBD. Research would benefit from investigating participation in MVPA as a coping strategy, in a longitudinal manner, to determine which modes of activity may be most beneficial to people with IBD.

Resistance training in young men induces muscle transcriptome-wide changes associated with muscle structure and metabolism refining the response to exercise-induced stress

Abstract: Gene expression is an important process underpinning the acute and chronic adaptive response to resistance exercise (RE) training. To investigate the effect of training status on vastus lateralis muscle global transcriptome at rest and following acute RE. Muscle biopsies of nine young men (age: 26(2) years; body mass: 69(9) kg; height 172(6) cm) who undertook RE training for 10 weeks were collected pre and 24 h post-RE in the untrained (W1) and trained (W10) states and analysed using microarray. Tests of differential expression were conducted for rested and after RE contrasts in both training states. To control for false discovery rate (FDR), multiple testing correction was performed at a cut-off of FDR < 0.05. Unaccustomed RE (at W1) upregulated muscle gene transcripts related to stress (e.g., heat shock proteins), damage and inflammation, structural remodelling, protein turnover and increased translational capacity. Trained muscles (at W10) showed changes in the transcriptome signature regarding the regulation of energy metabolism, favouring a more oxidative one, upregulated antioxidant- and immune-related genes/terms, and gene transcripts related to the cytoskeleton and extracellular matrix, muscle contraction, development and growth. These results highlight that chronic repetition of RE changes muscle transcriptome response towards a more refined response to RE-induced stress.

Reliability of a semi-automated algorithm for the vastus lateralis muscle architecture measurement based on ultrasound images.

Abstract: The assessment of muscle architecture with B-mode ultrasound is an established method in muscle physiology and mechanics. There are several manual, semi-automated and automated approaches available for muscle architecture analysis from ultrasound images or videos. However, most approaches have limitations such as workload, subjectivity, drift or they are applicable to short muscle fascicles only. Addressing these issues, an algorithm was developed to analyse architectural parameters of the vastus lateralis muscle (VL). In 17 healthy young men and women, ultrasound images were taken five times on two different days during passive knee joint flexion. From the images, fascicle length (FL), pennation angle (PAN) and muscle thickness (MTH) were calculated for both test days using the algorithm. Interday differences were determined using a two-way ANOVA. Interday and intraday reliability were assessed using intraclass correlation coefficients (ICC) and root mean square (RMS) differences. FL, MTH and PAN did not differ between day one and two. The within day ICCs were above 0.94 for all tested parameters. The average interday ICCs were 0.86 for the FL, 0.96 for MTH and 0.60 for PAN. The average RMS differences between both days were 5.0%, 8.5% and 12.0% for MTH, FL and PAN, respectively. The proposed algorithm provides high measurement reliability. However, the interday reliability might be influenced by small differences in probe position between days.

Relationship between power–duration parameters and mechanical and anthropometric properties of the thigh in elite cyclists

Abstract: The curvature constant (W′) and asymptote (critical power; CP) of the power–duration relationship are important parameters for explaining cycling performance. Short-duration endurance cycling events rely more heavily on the W′; however, the full mechanistic underpinning of this parameter is yet to be determined. Evidence suggests both muscle volume and muscle strength may contribute to the magnitude of W′. Therefore, the present study investigated the relationship between power–duration parameters (CP and W′) and (1) anthropometric and (2) mechanical properties of thigh muscles in a sample of elite cyclists. Eleven elite male cyclists had gross thigh volume (TVOL), quadriceps muscle volume (QVOL), vastus lateralis (VL) muscle pennation angle (PA) and VL muscle thickness (MT) measured. Additionally, maximum torque production of the knee extensors (FMAX) was assessed. The relationship between these anthropometric and mechanical measures and both the CP and W′ were determined. W′ showed a very strong positive and significant relationship with FMAX (r = 0.87, p < 0.001) and a large positive and significant relationship with TVOL (r = 0.60, p = 0.05). No other anthropometric characteristics were related to the W′. The CP was not associated with any mechanical or anthropometric parameter. In addition to muscle size, the maximal evocable force of a muscle (group) appears to be linked to the magnitude of the W′ in elite cyclists.

Do acute effects of exercise on vascular function predict adaptation to training

Abstract: No previous study has explored the importance of exercise-induced changes in vascular function to prolonged adaptations. Therefore, the purpose was to explore the within-subject relationship between the acute post-exercise change in brachial artery endothelial function (flow-mediated dilation, FMD) and the change in resting FMD after a 2-week exercise training in healthy volunteers. Twenty one healthy, young men (24 ± 5 years) underwent assessment of brachial artery FMD using high-resolution ultrasound before and after 30-min of moderate-intensity cycle exercise (80% maximal heart rate). Subsequently, subjects performed five 30-min cycle exercise bouts at 80% maximal heart rate across a 2-week period, followed by repeat assessment of resting brachial FMD post-training. Correcting for changes in diameter and shear, FMD did not change after the initial exercise bout (P = 0.26). However, a significant correlation was found between post-exercise changes in FMD and adaptation in resting FMD after training (r = 0.634, P = 0.002), where an acute decrease in post-exercise FMD resulted in a decrease in baseline FMD after 2 weeks and vice versa. We also found a positive correlation between antegrade shear rate during exercise and change in FMD% after acute exercise and after exercise training (r = 0.529 and 0.475, both P < 0.05). Our findings suggest that acute post-exercise changes in vascular function are related to changes in resting FMD after a 2-week endurance exercise training period in healthy men, an effect that may be related to exercise-induced increases in antegrade shear rate. This provides further insight into the relevance of acute changes in shear and FMD for subsequent adaptation.

Determining the potential sites of neural adaptation to cross-education: implications for the cross-education of muscle strength.

Abstract: Cross-education describes the strength gain in the opposite, untrained limb following a unilateral strength training program. Since its discovery in 1894, several studies now confirm the existence of cross-education in contexts that involve voluntary dynamic contractions, eccentric contraction, electrical stimulation, whole-body vibration and, more recently, following mirror feedback training. Although many aspects of cross-education have been established, the mediating neural mechanisms remain unclear. Overall, the findings of this review show that the neural adaptations to cross-education of muscle strength most likely represent a continuum of change within the central nervous system that involves both structural and functional changes within cortical motor and non-motor regions. Such changes are likely to be the result of more subtle changes along the entire neuroaxis which include, increased corticospinal excitability, reduced cortical inhibition, reduced interhemispheric inhibition, changes in voluntary activation and new regions of cortical activation. However, there is a need to widen the breadth of research by employing several neurophysiological techniques (together) to better understand the potential mechanisms mediating cross-education. This fundamental step is required in order to better prescribe targeted and effective guidelines for the clinical practice of cross-education. There is a need to determine whether similar cortical responses also occur in clinical populations where, perhaps, the benefits of cross-education could be best observed.

l-Menthol mouth rinse or ice slurry ingestion during the latter stages of exercise in the heat provide a novel stimulus to enhance performance despite elevation in mean body temperature

Abstract: This study investigated the effects of l-menthol mouth rinse and ice slurry ingestion on time to exhaustion, when administered at the latter stages (~ 85%) of baseline exercise duration in the heat (35 °C). Ten male participants performed four time to exhaustion (TTE) trials on a cycle ergometer at 70% Wmax. In a randomized crossover design, (1) placebo-flavored non-calorific mouth rinse, (2) l-menthol mouth rinse (0.01%), or (3) ice ingestion (1.25 g kg−1), was administered at 85% of participants’ baseline TTE. Time to exhaustion, core and skin temperature, heart rate, rating of perceived effort, thermal comfort and thermal sensation were recorded. From the point of administration at 85% of baseline TTE, exercise time was extended by 1% (placebo, 15 s), 6% (l-menthol, 82 s) and 7% (ice, 108 s), relative to baseline performance (P = 0.036), with no difference between l-menthol and ice (P > 0.05). Core temperature, skin temperature, and heart rate increased with time but did not differ between conditions (P > 0.05). Thermal sensation did not differ significantly but demonstrated a large effect size (P = 0.080; $$\eta _{{\text{p}}}^{2}$$ = 0.260). These results indicate that both thermally cooling and non-thermally cooling oral stimuli have an equal and immediate behavioral, rather than physiological, influence on exhaustive exercise in the heat.

Mental fatigue does not alter performance or neuromuscular fatigue development during self-paced exercise in recreationally trained cyclists.

Abstract: The purpose of this study was to investigate the effects of mental fatigue, characterized by a subjective feeling of tiredness, on the development of neuromuscular fatigue during a 4-km cycling time trial (4-km TT) Eight recreationally trained male cyclists performed a 4-km TT after either performing a prolonged cognitive task (mental fatigue) or after viewing emotionally neutral documentaries (control) The neuromuscular function of the knee extensors was assessed using electrical nerve stimulation at baseline, before (pre-TT), and after (post-TT) the 4-km TT Rating of perceived exertion (RPE) and physiological variables were periodically measured during 4-km TT Subjective ratings of fatigue increased significantly only after a prolonged cognitive task (P = 0022) Neuromuscular function at baseline was similar between conditions and remained unchanged at pre-TT Time to complete the 4-km TT was similar between control (376 ± 27 s) and mental fatigue (376 ± 26 s) There was no significant difference between conditions for RPE, $$~\dot {V}{{\text{O}}_2}$$ , $$\dot {V}{\text{E}}$$ , and HR throughout the exercise The 4-km TT-induced similar decrease (from baseline to post-TT) in maximal voluntary contraction (mental fatigue − 11 ± 10%, control − 16 ± 12%), twitch force (mental fatigue − 26 ± 16%, control − 24 ± 17%), and voluntary activation (mental fatigue − 5 ± 7%, control − 3 ± 2%) for both conditions Mental fatigue induced by prolonged cognitive task does not impair performance nor alter the degree of central and peripheral fatigue development during self-paced exercise in recreationally trained cyclists

Influence of full range of motion vs. equalized partial range of motion training on muscle architecture and mechanical properties.

Abstract: The purpose of this study was to determine the effect of a 15-week partial range of motion (ROM) resistance training program on the vastus lateralis (VL) architecture and mechanical properties, when the time under tension (TUT) was equalized Nineteen untrained male subjects were randomly assigned to a control (Control; n = 8) or training (TG; n = 11) group In the TG, the dominant and nondominant legs were randomly selected to be trained with a full ROM (FULL) or a partial ROM (PART) in an isokinetic dynamometer Training volume was equalized based on the TUT by manipulating sets and repetitions The VL muscle architecture was assessed by B-mode ultrasonography at rest and during maximal isometric knee extension contractions (MVCs) at ten knee angles The VL fascicle force and specific tension were calculated from the MVCs with superimposed stimuli, accounting for the moment arm length, muscle architecture, and antagonist coactivation The FULL training induced changes in fascicle length (FL) (49 ± 20%, P < 0001) and specific tension (258 ± 187%, P < 0001) There was a moderate effect of PART training on the physiological cross-sectional area (PCSA) (78 ± 40%, P < 0001, dav = 06) and torque–angle adaptations (average increase 177 ± 39%, P < 005) These results provide evidence that crucial architectural and mechanical muscle adaptations are dependent on the ROM used in strength training It seems that muscle FL and specific tension can be increased by pure concentric training if greater ROM is used Conversely, restricting the ROM to shorter muscle lengths promotes a greater PCSA and angle-specific strength adaptations

Validity of a triaxial accelerometer and simplified physical activity record in older adults aged 64-96 years: a doubly labeled water study.

Abstract: The aim was to examine the validity of a triaxial accelerometer (ACCTRI) and a simplified physical activity record (sPAR) in estimating total energy expenditure (TEE) and physical activity level (PAL) in older adults with the doubly labeled water (DLW) method. A total of 44 Japanese elderly individuals (64–96 years), of which 28 were community-dwelling healthy adults with or without sporting habits (S or NS group) and 16 were care home residents with frailty (F group), were included in the study. Basal metabolic rate (BMR) was measured by indirect calorimetry, TEE was obtained by the DLW method, and PAL was calculated as TEE/BMR. Daily step count was monitored by a pedometer (Lifecorder). The 24-h average metabolic equivalent was assessed by ACCTRI and sPAR. The TEEDLW in men was 2704 ± 353, 2308 ± 442, and 1795 ± 338 kcal d−1, and that in women was 2260 ± 208, 1922 ± 285, and 1421 ± 274 kcal d−1 for the S, NS, and F groups, respectively. ACCTRI and sPAR systematically underestimated actual TEE (− 14.2 ± 11.6 and − 15.3 ± 12.3% for ACCTRI and sPAR, respectively). After diet-induced thermogenesis was taken into account for ACCTRI and sPAR, TEEDLW was significantly correlated with TEEACCTRI (R2 = 0.714) and TEEsPAR (R2 = 0.668). PALDLW was also significantly correlated with PALACCTRI (R2 = 0.438) and PALsPAR (R2 = 0.402). Age, living conditions, frailty, and sporting habits contribute to TEE and PAL in the elderly population. ACCTRI and sPAR underestimated TEE and PAL, and adequate corrections are required. The corrected ACCTRI and sPAR are both useful tools to estimate TEE and PAL.